Lastly, I must mention the recent researches of Hideyo Noguchi,[14] with reference to the photodynamic action of _eosin_ and _erythrosin_ upon the venoms of the Cobra, _Vipera russellii_, and _Crotalus_. It was found by the scientist in question that the toxicity of these various venoms is more or less diminished in the presence of these aniline colours, when the mixtures are insolated. Cobra-venom is the most resistant, just as it is in regard to the other physical or chemical agents. That of _Crotalus_, on the contrary, is the least stable. CHAPTER VI. _THE PHYSIOLOGICAL ACTION OF SNAKE-VENOMS._ A.--PHYSIOLOGY OF POISONING IN MAN AND IN ANIMALS BITTEN BY THE DIFFERENT SPECIES OF POISONOUS SNAKES. (_Colubridæ; Viperidæ; Hydrophiidæ._) The bites of poisonous snakes produce very different effects according to the species of snake, the species to which the animal bitten belongs, and according to the situation of the bite. It is therefore necessary to take these various factors into account, in describing the symptoms of poisoning in different animals. When the quantity of venom introduced into the tissues by the bite of the reptile is sufficient to produce fatal results--which is happily not always the case--the venom manifests its toxic action in two series of phenomena: the first of these is local and affects only the seat and surroundings of the bite; the second, or general series, is seen in the effects produced upon the circulation and nervous system. It is remarkable to find how great is the importance of the local disorders when the venomous reptile belongs to the _Solenoglypha_ group (VIPERIDÆ), while it is almost _nil_ in the case of the _Proteroglypha_ (COLUBRIDÆ and HYDROPHIIDÆ). The effects of general intoxication, on the contrary, are much more intense and more rapid with the venom of _Proteroglypha_, than with that of _Solenoglypha_. In considering the usual phenomena of snake-poisoning in man, we must therefore take this essential difference into account, and draw up separately a clinical description of the symptoms observed after a bite from a _Cobra_ (COLUBRIDÆ), for instance, and another list of those that accompany a bite from _Lachesis_ or _Vipera berus_ (VIPERIDÆ). The bite of a _Cobra_, even of large size, is not very painful; it is characterized especially by numbness, that supervenes in the bitten part, rapidly extends throughout the body, and produces attacks of syncope and fainting. The patient soon experiences a kind of lassitude and irresistible desire to sleep; his legs scarcely support him; he breathes with difficulty and his respiration becomes of the diaphragmatic type.